Some solid electrolytic capacitors are used for removing noise generated in a device such as a CPU and also for stabilizing power supply to an electronic apparatus (see patent document 1 cited below). FIG. 25 of the present application shows an example of such solid electrolytic capacitor. The solid electrolytic capacitor X includes a porous sintered body 90 made of a metal material that performs a valve action (such metal is referred to as “valve metal” below). An anode wire 91 is disposed such that a portion thereof intrudes into the porous sintered body 90, and that the remaining portion of the anode wire 91, sticking out of the porous sintered body 90, constitutes an internal anode terminal 91a. On the porous sintered body 90, a conductive layer 92 serving as a cathode is provided. Conductors 93, 94 are electrically connected to the internal anode terminal 91a and the conductive layer 92 respectively, and a portion of the respective conductor exposed out of an encapsulating resin 95 constitutes an external anode terminal 93a and an external cathode terminal 94a for surface mounting. Here, the impedance Z of the solid electrolytic capacitor is expressed by the following formula.Z=√{square root over ((R2+(1/ωC−ωL)2))}  [Formula 1](ω: 2πf (f: frequency), C: capacitance, R: resistance, L: inductance)
As is understood from Formula 1, 1/ωC is predominant in a low-frequency region where the frequency is lower than the self-resonance point, whereby an increase in capacitance of the solid electrolytic capacitor X reduces the impedance. In a high-frequency region near the self-resonance point, the resistance R is predominant, and hence it is desirable to reduce the equivalent serial resistance (hereinafter, ESR) of the fixed electrolytic capacitor X. Further, since ωL is predominant in an ultra-high-frequency region where the frequency is higher than the self-resonance point, it is required to reduce the equivalent serial inductance (hereinafter, ESL) of the solid electrolytic capacitor X.
Recently, there has been a growing demand for a larger capacitance of the power supply. The solid electrolytic capacitor X also need to have a larger static capacitance, and to this end, it is desirable to increase the dimensions of the porous sintered body 90. However, the larger the porous sintered body 90 is, the more difficult it becomes to attain a uniform density for the manufactured sintered body. Unfavorably, nonuniform density leads to difficulty in forming a dielectric layer (not shown) or a solid electrolytic layer (not shown) in the pores of the sintered body 90. Another drawback is that the porous sintered body 90 and the anode wire 91 fail to be securely bonded to each other.
A device such as a CPU with a high-speed clock generates a high-frequency noise containing harmonics components. Higher operation speed and digitization of electronic apparatuses require for a power source capable of exhibiting quick response. The solid electrolytic capacitor X, used in such circumstances, is under a strong requirement to have a minimized ESL. Minimizing the ESL may be attained by employing a plurality of anode wires 91. When the inductance of components such as the conductors 93, 94 is large, however, it is impossible to satisfy the foregoing requirement, and therefore still there is a room for improvement with respect to reducing the ESL of the solid electrolytic capacitor X as a whole.
Patent document 1: JP-A-2003-163137